不同覆岩地层正断层下盘煤层开采地表下沉规律

Surface subsidence laws of footwall coal seam mining of normal fault under different overburden strata

断层破坏覆岩地层的整体性,影响岩土体的强度特性和变形性质,导致开采沉陷规律更为复杂。为研究不同覆岩地层与正断层共同影响下煤层开采地表沉陷规律,构建不同覆岩地层正断层下盘煤层开采覆岩运动与地表变形的理论模型,数值模拟分析不同覆岩地层正断层下盘煤层开采地表下沉规律与特征,结合实例进行了对比分析。结果表明:地表移动变形范围与松散层厚度密切相关,随松散层厚度的增加,相较于无断层一侧,地表下沉盆地在断层一侧的移动变形范围先减小后扩大再减小,最终与无断层一侧相同;厚基岩地质条件下,随松散层厚度增加,地表产生裂缝的位置由断层露头先向采空区偏移后向断层上盘偏移;厚松散层地质条件下,松散层吸收了断层诱发的非连续变形,随松散层厚度增加,地表由偏态下沉盆地逐渐变为对称的下沉盆地。

The fault destroys the integrity of the overburden strata and affects the strength and deformation properties of the rock mass,resulting in more complex mining subsidence laws.To study the surface subsidence law of coal seam mining under the joint influence of different overburden strata and normal faults,a theoretical model of overburden rock movement and surface deformation of coal seam mining under normal faults in different overburden strata was firstly constructed.Then,the mining subsidence laws and characteristics were analyzed by conducting numerical simulation experiments.Lastly,a comparative analysis was carried out with examples.The results show that the range of surface movement and deformation is closely related to the thickness of the unconsolidated layer.Compared with the non-fault side,the movement and deformation range of the subsidence basin on the fault side first decreases,then expands,then decreases again,and finally becomes the same as the non-fault side along with the increase of the thickness of the unconsolidated layer.Under the geological conditions of thick bedrock,the position of the cracks on the surface first migrates from the fault outcrop to the gob and then migrates to the fault hanging wall as the thickness of the unconsolidated layer increases.Under the geological conditions of thick unconsolidated layer,the surface gradually changes from a skewed subsidence basin to a symmetrical subsidence basin with the increase of the thickness of the unconsolidated layer due to its absorption of the discontinuous deformation induced by the fault.